Trigonometrical Survey. 



6S S 



The angle at Danbury, between Southweald and Hatfield Broad Oak, was found to be 

 54 44' 30". The distances from Danbury to Southweald and Hatfield Broad Oak have 

 been already found, the former being 77622 feet, and the latter 85096 feet; from these 

 we get the triangle, 



Danbury - 54 44' 30" 



Southweald - 67 42 5 



Hatfield Broad Oak 57 33 25, which gives 75104 feet, for the 

 distance between Hatfield Broad Oak and Southweald Steeples. 



In order to connect the preceding triangles with those carried on for the survey of the 

 south-western part of Essex, and of Hertfordshire, stations were selected on Hampstead 

 Heath, and on Highbeech in Epping Forest, to which the great theodolite was taken, as 

 related in the article detailing the particulars of the operations in 1799. The triangles 

 making this connection are the following. The first, namely, 



Severndroog Tower 2 8° 58' 10" 



Southweald - 94 49 5 



Langdon Hill - 56 12 45, is had from the included angle 

 at Severndroog Tower, 28 58' 10", and the sides Severndroog Tower and Southweald, 

 Severndroog Tower and Langdon Hill : the first is 73787 feet, and the second 88470 feet. 

 From these data, we obtain the distance between the station on Langdon Hill and that on 

 Southweald Steeple zz 43001 feet. 



Names of Stations. 



Observed 

 angles. 



Distances. 



Severndroog Tower 

 Langdon Hill 

 Brentwood Steeple 



1 n 



24 24 35 

 62 26 39 



!• Brentwood 



{ 



Feet. 



78553* 

 36616 



Severndroog Tower 



Southweald 



Brentwood 



4 33 29 

 125 53 12 



> Brentwood 



{ 



78553* 

 7706 



Foot of the cross on the dome of St. Paul's from the station on Severndroog Tower 39962*. 



Phil. Trans, for 1787. p. 250. 





33 53 4 

 51 24 12 



> Highbeech 







Severndroog Tower 



St. Paul's ... 



Uigbbeecb 



{ 



71534 

 61919 



Severndroog Tower 



Highbeech ... 



Southweald 



44 34 28 

 6 9 53 13 



>Southweald 



{. 



73795* 

 55156 



MDCCC. 



IT 



